The Best Bitcoin Hardware Wallets & Seed Phrase Backup Tools
A simple directory of the best Bitcoin signing devices, metal seed backup tools, and supporting wallet software — because your sats are best stored cold.
COLDCARD Mk4
Bitcoin-only hardware signing device with dual secure elements, USB-C, NFC, and air-gapped MicroSD signing. Made by Coinkite. (Discontinued — superseded by Mk5.)
The COLDCARD Mk4 is Coinkite's fourth-generation Bitcoin-only hardware signing device, widely regarded as a milestone in air-gapped Bitcoin security. It features dual secure elements (Microchip ATECC608 + Maxim DS28C36B), a 128x64 OLED display, a numeric keypad, a sliding protective cover, and connectivity via USB-C, NFC tap, microSD card, and virtual disk mode. Security features include an anti-phishing PIN system with unique word verification, a genuine/caution LED controlled by dedicated circuitry, a clear case option to detect hardware implants, dice-roll seed generation, and multiple PIN modes including Duress PIN, Brick PIN, and Login Countdown. Supports BIP39 passphrase (25th word), PSBT (BIP174), and NFC Push Transaction (PushTx). The Mk4 has been discontinued and is no longer available from the official Coinkite store — it has been superseded by the COLDCARD Mk5.
